This invention relates to a beverage dispensing system and is particularly concerned with such a system wherein a gas selected from carbon dioxide, nitrogen (or other inert gas) and air is injected into the beverage during dispensing, for example to form or assist in the formation of a head or froth on the beverage as dispensed and to ensure that the dispensed beverage may have a dissolved gas content according to consumer preference. The present invention was primarily developed for use in the dispensing of fermented beverage such as beer, lager, stout, wine and cider but may be used to advantage in the dispensing of non-fermented beverage or so-called soft drinks.
Our G. B. Patent Specification No. 1,063,753 discloses a system in which the beverage is dispensed through a supply passage under control of a valve, the beverage being derived from a bulk container. An injector is provided for introducing gas under pressure into the beverage in the supply passage remotely from the bulk container and during dispensing so that such injected gas forms or assists in the formation of fine bubbles to develop a head of foam on the dispensed beverage. The beverage in the bulk container may have gas dissolved therein and be withdrawn from that container with a headspace of that gas; alternatively the beverage in the bulk container may, for practical purposes, be considered as having no gas dissolved therein so it is substantially flat. In either event the gas which is injected into the beverage during dispensing may ensure that the beverage as dispensed will have a gas content which, for a particular beverage, is regarded as desirable in providing the flavour and head characteristics required of that beverage. Accordingly, it is desirable that the injector admits consistent predetermined quantities of the gas to the beverage being dispensed to ensure that the system, once set up for a particular beverage, will provide predetermined and constant characteristics for the beverage as dispensed. In our prior proposal the gas was introduced to the beverage by way of a needle valve and an injector nozzle--the former serving to adjust the gas pressure to the nozzle; however, experience has shown that with this arrangement the beverage as dispensed could have inconsistent characteristics, possibly resulting from an inconsistency in the flow of the gas which was introduced (perhaps due to the coarseness in the control of the needle valve and the inconsistent gas flow characteristics through that valve). Accordingly, there is still a requirement for a relatively simple and inexpensive beverage dispensing system by which one or more of an inert gas, nitrogen/air and carbon dioxide gases can be introduced into the beverage during dispensing and which alleviates the disadvantages of the prior proposals. It is an object of the present invention to satisfy this requirement.